Advanced Locking Plate System

ALPS

“Biological internal fixation” involves the use of locked internal fixators, which have minimal implant-to-bone contact, long-span bridging and fewer screws for fixation.[1] The Advanced Locking Plate System (ALPS)* is a biological internal fixation system that was designed from the beginning to protect the bone, provide stability and promote rapid healing.

The ALPS plating system builds on research and development work done on the PC-Fix (Point Contact Fixitor) in the 1980’s and 1990’s at the AO Research Institute, Davos, Switzerland. Numerous publications have documented the PC-Fix design and clinical results. Please see the Reports section for references. Currently an in vitro study comparing ALPS plates with other plates is ongoing at the Cummings School of Veterinary Medicine at Tufts University. Results will be referenced once the study is complete and published.

Increased resistance to infection and faster, more consistent healing are all but certain benefits to come from clinical applications. Versatility of the plates with bending in both planes, as well as their geometry optimized for strength and soft tissue cover, are also considered worthwhile improvements over state of the art in internal fracture fixation. By the end of 2009, the ALPS had been used in over 1,000 dogs and cats by more than 50 surgeons in Europe, the Americas, and Japan.

Principles

MAIN DESIGN OBJECTIVES

1. Minimize vascular damage to both periosteum and endosteum;
2. Allow adaptation in both planes, yet exceed the strength of conventional plates;
3. Accept both regular and locking screws in all holes;
4. Use superiorly biocompatible titanium and titanium alloys.

Vascular damage is minimal because:

The underside of ALPS plates allows for only very small contact areas to the bone, reducing compression of periosteal blood vessels; and

The endosteal blood supply is spared through preferred use of locking, monocortical screws – drilling depth is controlled with a drill stop limiting vascular damage within the medullary canal.

Adaptation to bone geometry by bending in both planes is facilitated by:

The computer-optimized shape of the plate, resembling the early Sherman plate; and

The use of unique bending pliers for in-plane bending and modified bending irons for out-of-plane bending, designed to protect the holes.

Geometry of the screw heads and of the screw holes permit use of either:

Conventional bone screws, with ±30° longitudinal and ±5° transverse swivel, either in neutral or compression mode. The screw holes are tapered to squeeze the screw heads, preventing unscrewing; and

Locking screws, preferred as long as the cortex thickness is sufficient – near the joints one can use either longer locking screws, or conventional bicortical ones.

ALPS uses only titanium or titanium alloys for all of its implants:

They allow bone and soft tissue to make a close, adhering contact at the interfaces, preventing formation of a fluid filled gap – a major risk for seeding and spread of infection; and

Their superior mechanical properties, with a favorable tradeoff between ductility and strength.

Highly advanced manufacturing technologies used by KYON suppliers to produce the implants and instruments of the ALPS have given us an opportunity to provide veterinary surgeons with the most advanced, yet affordable plating system.

CHARACTERISTICS:

• ALPS plates minimize contact with the periosteum and thus reduce the iatrogenic insult to bone perfusion common with conventional compression plates

Development

Vascular Damage in Fracture Plating: An Introduction

In the late seventies and early eighties, in vivo experimental animal studies produced convincing evidence that early temporary porosis, commonly observed under conventional bone plates, resulted from an insult to periosteal blood circulation caused by implant-bone contact. Deprived of blood perfusion, the bone turned necrotic, then sclerotic, before undergoing remodelling through neovascularization. The result was early, frequently persistent porosis. While in most cases, the end result was still bony union, many of the major complications of internal fixation can be linked to the vascular damage caused by surgical intervention and the implants used. Infection tops the list.

Reducing Vascular Damage: Methods

Two engineering proposals from the Straumann Institute, Waldenburg, provided early leads:

In vivo testing of the Brunner plate provided some of the most convincing evidence linking bone remodelling to perfusion damage. Sutter’s in vitro testing of the locked vs. conventional plates demonstrated the mechanical advantages of locked screws.

Research & Development: PC-Fix to LC-DCP

Combining the two proposals with a novel technique, locking the screw by means of friction between a conical head and a conical hole in the plate, Dr. Slobodan Tepic initiated the development of a new plating system, PC-Fix, or Point Contact Fixator, by AO.

Approximately eight years of testing on animals demonstrated some anticipated and some surprising advantages of PC-Fix when compared to conventional plating:

PC-Fix was then taken into the clinical setting in both human and veterinary applications. A large, multi-centre clinical trial on forearm fractures largely met the expectations, but the system was never commercialized.

Elucidation, of the role played by vascular damage resulting from internal fixation plates, provided fertile ground for innovation in the past three decades. A spur of activity, in R&D and marketing in the eighties, resulted in the release of the Synthes LC-DCP system. LC-DCP featured a modification in design and established titanium as the metal of choice, but the surgical principles of application remained the same. While the PC-Fix system was never commercialized, the locking screw principle caught the attention of both the industry and the surgical community. Within a very short period of time, locking has become a standard feature on just about every internal fixation system. Technical solutions also proliferated, but the main message of the research that started it all — the crucial role of blood perfusion in the process of healing – was still looking for an audience.

Moving Forward: The Advanced Locking Plate System (ALPS)

Dr. Tepic, who conducted the research on PC-Fix, developed the Advanced Locking Plate System (ALPS) as a “biological internal fixation” [1] system, designed from conception to preserve the vascular supply, increase resistance to infection and accelerate healing. “Biological internal fixation” involves the use of locked internal fixators, which have minimal implant-to-bone contact, long-span bridging and fewer screws for fixation.

ALPS has not been used on any experimental animals, nor has it been tested in a clinical trial, but its main features related to the bone contact and fixation method are very similar to PC-Fix, suggesting that most, if not all of the observations from the PC-Fix project are highly relevant to ALPS, and specifically those related to infection.

The ALPS plate is a combination of Shermann (1907) and Brunner plates, with holes, providing for use of either conventional or locking screws. The shape of the plate allows for bending in both planes. The plate material is c.p. titanium; for the screws, titanium alloy. Finite Element Analysis was used to optimize the shape of the plate. Three sizes, designated by the width of the plate (5, 8 and 10mm), suitable for small animals are currently available, with additional sizes coming soon. Since ALPS’ commercial release in the spring of 2007, 50 surgeons have used ALPS on over 1,000 clinical cases. Anecdotal evidence is positive. Increased resistance to infection and faster, more consistent healing are all but certain benefits to come from further clinical applications.

Currently, an in vitro study, comparing ALPS plates with other plates, is ongoing at the Cummings School of Veterinary Medicine at Tufts University. Results will be referenced once the study is complete and published. Advanced Locking Plate System is patented/patent pendingback to top Λ

Instructions

Use a core diameter drill bit for the hole to be tapped

Use the outer diameter drill bit with the double sleeve guide for the lag hole

The nose on the core diameter drill sleeve limits the range of the swivel

Use the compression sleeve to achieve dynamic fracture compression with regular screws

Use the locking screw sleeve to drill for locking screwsLocking screws are only installed perpendicular to the plate

Before drilling adjust the drill stop position to avoid unintended far side drill penetration

The drill should protrude from the sleeve by 2mm more than the screw length

It is preferable to use locking screws

Use the lag screws at their best position, do not insist on lagging through the plate

Always attempt to place a transverse undercut over the fractureAvoid placing screws too close to the fracture

Double plating with ALPS is an admissible alternative to lagging

For the second plate, a plate one size smaller and shorter is preferred

Proper placement of the plate in the bending irons for concave bending

For best control and ease of use, pull apart the ends of the irons

Proper placement of the plate in the bending irons for convex bendingProceed hole-to-hole for sharp bends
Use plugs for excessive bends

Caution! Avoid bending plates back-and-forthTitanium does not tolerate cycling in the plastic range as well as stainless steel

For in-plane bending use the special bending instrument

Close the handles, drop the plate between the cylinders and pull the handles apart to bendFor most applications, only a slight in-plane bend is indicated